Cost & Energy calculator
Electricity Cost Calculator
This calculator estimates electricity cost from load power or known kWh, average operating hours, billing days, and the electricity rate in $/kWh. Enter your own usage pattern to produce the daily, monthly, and annual cost for that scenario.
Updated July 16, 2026
Enter watts or kWh, average daily hours, billing days, and your $/kWh rate to estimate daily, monthly, and annual electricity cost.
Monthly cost uses load power, operating time, billing period, and the effective utility rate from your bill.
Enter load watts, daily hours, billing days, and your utility rate
Calculator Inputs
Quick Presets
Calculation Results
Enter values above to see calculation results
Field kit
Tools for energy cost checks
Use the cost estimate as a budget screen, then compare plug-in meters that can capture real appliance energy use.
Compare plug-in metersFor measured kWh useOpens in a new tabFind energy smart plugsFor appliance trackingOpens in a new tab
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Calculation history
Example Calculations
More examples. Open to review 1 additional calculation example.
How to Use
How the electricity cost calculator works
The tool uses the standard relationship Energy (kWh) = Power (kW) × Time (hours) and then multiplies the result by your electricity rate. It is intended for practical bill screening, appliance planning, and quick operating-cost checks.
Use the calculator before relying on a sample cost
For a direct kWh cost estimate, convert watts to kilowatts, multiply by daily hours and billing days, then multiply by the rate. The result depends on the actual load, run time, billing period, and utility rate you enter above.
Core formulas
- Load in kW = Watts ÷ 1000
- Daily energy = kW × hours per day
- Monthly energy = daily energy × billing days
- Daily, monthly, and annual cost = energy × electricity rate
What to enter before you calculate
- Load power: Enter the average running watts for one appliance or the combined watts for a group of loads.
- Average hours per day: Use a realistic operating average rather than a best-case or worst-case day.
- Billing days: Match the number of days in the utility bill or estimate window you want to review.
- Electricity rate: Use the effective $/kWh from your U.S. utility bill when possible. If you have time-of-use pricing, run separate peak and off-peak scenarios.
Typical load examples
| Load | Typical Running Power | Typical Daily Use | Planning Note |
|---|---|---|---|
| Portable space heater | 1,500 W | 2-8 hours | Resistance heat is usually close to rated watts while operating |
| Refrigerator | 120-250 W average running load | Continuous cycling | Use average running load, not compressor start current |
| Window air conditioner | 900-1,500 W | 4-12 hours | Run a summer scenario separately if usage is seasonal |
| Level 2 EV charging | 3,800-11,500 W | 1-4 hours | Use the charger output or actual charging power at the vehicle |
| Lighting circuit | 50-600 W | 2-10 hours | Enter total connected lighting watts for the area you want to review |
What this calculator includes and what it does not
This page estimates the energy-charge portion of the bill. It does not automatically add fixed customer charges, taxes, riders, or demand charges. If your tariff has time-of-use pricing, demand billing, or seasonal blocks, run separate scenarios or confirm the final estimate against the actual utility statement.
For grouped appliance review, you can add running watts and use the combined value here. For equipment-by-equipment comparison, use the Appliance Energy Calculator. If you want a general kWh model first, use the Energy Calculator. For project savings screening, continue with the Energy Savings ROI Calculator.
Common Applications
More applications. Open to review 3 additional use cases.
Frequently Asked Questions
How do I calculate monthly electricity cost from watts?
Convert watts to kilowatts by dividing by 1000, multiply by average hours per day, multiply by the number of billing days, and then multiply by the electricity rate. Use the calculator fields for the actual load, schedule, and utility rate instead of relying on a generic example.
Should I use nameplate watts or measured running watts?
Measured or average running watts are preferred whenever possible. Many appliances cycle or operate below nameplate input during normal use, so using locked-rotor, startup, or maximum input values can overstate annual cost.
Can I use this calculator for more than one device?
Yes. Add the running watts of the loads you want to review and enter the combined value as one total. That gives you a grouped estimate using the same hours, billing days, and electricity rate.
Does this calculator include utility fixed fees or demand charges?
No. It estimates the energy-charge portion of the bill based on kWh. Fixed customer charges, taxes, riders, demand charges, and power-factor penalties must be reviewed separately from the actual tariff and utility bill.
How should I handle time-of-use rates?
Run separate scenarios for each rate period. For example, if part of the load runs during off-peak hours and part runs during peak hours, calculate each block separately and add the results. This keeps the estimate closer to a real U.S. utility bill.
Why might my bill still differ from the estimate?
Actual bills can include seasonal tariffs, minimum charges, fixed fees, taxes, and rate adjustments that are outside a simple kWh model. The estimate is most useful for screening, budgeting, and comparing loads rather than reproducing every line item on the bill.
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